1. Field of the Invention
The present invention relates to optical monitoring devices that monitor the quality of an optical signal passing through an optical cable. More particularly, the present invention relates to optical monitoring devices that monitor the quality of signals on multiple optical fibers using an optical switching mechanism and a single monitoring device.
2. Description of the Prior Art
There are many applications that utilize an optical fiber network to establish optical communications between a host digital terminal (HDT) at a central office and an optical network unit (ONU) at a remote location. Since a central office serves as the point of origin for the optical fibers in the optical fiber network, fiber administration systems are typically used at the central office to manage the flow of optical signals as they are directed to the various ONUs along the different optical fibers in the network.
In many fiber administration systems, as the optical fibers in a network enter the central office, they are directed into an optical distribution frame where the individual optical fibers are terminated in an organized manner. Such fiber administration systems are exemplified by the LGX.RTM. fiber administration system which is currently manufactured by Lucent Technologies of Murray Hill, New Jersey, the assignee herein. In such fiber administration systems, the optical distribution frames used at the central office are typically large structures that are arranged in parallel rows. Each optical distribution frame is commonly mounted between the floor and ceiling and only a few feet separate each row of frames.
Each optical distribution frame located at the central office typically defines a plurality of bays, wherein each bay houses several fiber distribution shelves. On each of the fiber distribution shelves are optical couplings that receive the ends of all of the individual optical fibers that enter the central office and are contained within the optical fiber network. By terminating each optical fiber at a coupling on one of the different fiber distribution shelves, the location of each optical fiber becomes known within the overall assembly. Once terminated at a known address on one of the fiber distribution shelves, each optical fiber can be selectively coupled to a HDT or a variety of other pieces of optical equipment located at the central office.
Within the fiber administration system it is desirable to monitor the signal quality of optical signals in a variety of different optical fibers. In order to monitor such optical signals, the optical signals must be converted to electrical signals. The electrical signals can then be automatically monitored by a processor under computer control that uses statistical process control software. One problem associated with monitoring various optical signals in a fiber administration system is space. Fiber administration systems are modular in design, wherein different pieces of hardware are designed to fit within one of the shelves in the frame of the fiber administration system. The space dedicated to one shelf in a fiber administration system is small. This leaves little room for complex monitoring systems and numerous optical leads.
A need therefore exists for a optical fiber monitoring apparatus that is small enough to fit in a shelf of a fiber administration system, yet is capable of monitoring numerous optical fibers within that confined space.